天气噪声对大西洋经向翻转环流变异的作用

Recent studies suggest that the primary (internal) source of predictability on decadal timescales in the North Atlantic is the AMOC. In many coupled climate models the AMOC exhibits decadal oscillations, which can be considered as one possible physical basis for decadal climate prediction. However, there is as yet no clear understanding of the causes for the AMOC oscillations in either the models or observations. An issue highly pertinent to the understanding of decadal climate predictability and to the discussion of the role of oceans in climate change is by what and how the AMOC oscillations are sustained. This proposal represents a systematic approach toward understanding this important issue. In particular, we seek to explore how the mean strength and variability of the AMOC are affected by "weather noise", through what physical processes "weather noise" exerts its influence on the AMOC, and what the role of "weather noise" is AMOC's response to global climate change. A set of carefully designed numerical experiments through the use of a novel noise filtering algorithm, called interactive ensemble (IE), will be conducted and thoroughly analyzed to test the following scientific hypotheses: 1) "Weather noise" through its effect on ocean mixing and deep-water formation processes plays a key role in AMOC variability as well as in maintaining its mean strength; 2) "Weather noise" changes in response to global warming may contribute significantly to projected AMOC changes under global warming scenarios.

大西洋经向翻转环流（AMOC）的年代际振荡与北大西洋表层海温年代际尺度的可预报性有着密切的关系，然而目前对这种振荡的原因却不是很清楚。作为理解年代际气候可预报性以及海洋在气候变化中的作用的重要议题之一，AMOC及其振荡激发和维持的物理机制就成为一个亟待研究的命题。本项目拟利用一个全球高分辨率海气耦合模式和新开发的交互集合技术（Interactive Ensemble）深入系统的研究"天气噪声"对AMOC强度和变异的影响，特别是其中起作用的重要的物理过程以及对未来气候变化的响应问题。通过一系列数值试验和结果分析，预期可以验证；1）"天气噪声"可以通过影响海洋混合和深层水形成来维持和影响AMOC的强度及变异；2）"天气噪声"对气候变暖的响应可以有助于预测未来气候变暖情景下的AMOC变化。本项目还将利用其他相关资料对上述预期成果展开进一步的验证。

大西洋经向翻转环流（AMOC）是全球海洋环流的重要组成部分，同时也是气候系统的重要驱动力量。课题主要探究了天气系统对AMOC的作用，同时利用耦合环流模式验证大气内部产生的高频的天气尺度的天气变化对AMOC强度及变化的影响。利用新的耦合技术得到的结果表明，天气尺度的大气变化信号被抑制后，AMOC的强度和变化都有很大的减弱。天气变化对高纬度海区的深对流活动具有强烈影响，而深对流的强弱与AMOC的强度和变化有紧密联系。数值模拟的结论验证了天气尺度的气候系统在维持AMOC强度和变化过程中起到重要作用。大气的天气变率和AMOC的相互作用是全球气候系统中的重要反馈机制，在今后的气候变化研究中需要考虑此反馈机制的影响和作用。.课题基本按照任务书计划进行，达到了预期目标，研究结果对大西洋AMOC的研究和气候预测具有一定的价值，可为下一步深入研究打下初步的基础；在相关学术刊物上已发表论文12篇（含接收1篇），其中SCI论文4 篇。